摘要:自20世纪初人类发明并掌握工业合成氨的技术以来，氮肥施用量迅速增长。在一部分国家或地区，氮肥的施入量已经超过作物对氮素的需求，导致大量氮素损失到环境中，造成氨挥发、氧化亚氮排放、地下水硝酸盐污染等环境问题。土壤在微生物的作用下可以通过反硝化、厌氧氨氧化等过程将活性氮素转化为惰性氮气，达到清除过多活性氮的目的。由于大气中氮气背景浓度太高，因此很难直接准确测定土壤的氮气排放速率，导致土壤氮气排放通量、过程与调控机制研究远远落后于土壤氮循环的其他方面。本文综述了土壤氮气排放主要途径（反硝化、厌氧氨氧化与共反硝化）及其对土壤氮气排放的贡献；测定土壤氮气排放速率的方法（乙炔抑制法、氮同位素示踪法、N2/Ar比率-膜进样质谱法、氦环境法与N2O同位素自然丰度法）及其优缺点；调控土壤氮气排放通量的主要因素（氧气、可溶性有机碳、硝酸盐、微生物群落结构与功能基因表达等）及其相关作用机制。最后指出研发新的测定原位无扰动土壤氮气通量的方法是推进本领域相关研究的关键；定量典型生态系统（如旱地农田、稻田、森林、草地与湿地）土壤氮气排放通量，阐明其中的微生物学机制，模拟并预测土壤氮气排放对全球变化的响应规律是本领域的研究热点与发展方向。
关键词:土壤/
氮气排放/
反硝化/
厌氧氨氧化/
氧化亚氮排放/
氮损失
Abstract:The amount of applied nitrogen fertilizer has increased dramatically since the invention of the industrial ammonia synthesis in the early 20th century. In some countries or regions, the amount of nitrogen fertilizer input has exceeded crop nitrogen demand. This has led to a large amount of nitrogen losses to the environment, causing environmental pollution such as ammonia volatilization, nitrous oxide emission and groundwater contamination. Soil microbes can transform active nitrogen into inert dinitrogen and consequently remove superfluous nitrogen from soil via denitrification and anammox. Direct and precise measurement of soil denitrification has been a continuous challenge due to high background concentration of atmospheric dinitrogen, which has hindered progress in research on soil dinitrogen emissions. This paper reviewed the main pathways of soil dinitrogen emission[denitrification, dissimilatory nitrate reduction to ammonium (DNRA) and co-denitrification] and their contributions to soil dinitrogen emission. It also covered the methods of soil dinitrogen flux determination (acetylene inhibition technique, 15N tracing method, N2/Ar membrane-inlet mass spectrometry, helium environment method and natural abundance 15N2O isotopic method) and their advantages, disadvantages. The key factors regulating soil dinitrogen emission (oxygen, dissolved organic carbon, nitrate, microbial community structure and functional gene expression) and the related mechanisms were also summarized. In conclusion, it was essential to develop new methods for in situ dinitrogen flux determination in undisturbed soils. More studies were needed to quantify soil dinitrogen flux in typical ecosystems (such as dryland, farmland, forest, grassland and wetland), clarify microbial mechanism involved, and simulate and predict the responses of soil dinitrogen emission to global change.
Key words:Soil/
Dinitrogen emission/
Denitrification/
Anaerobic ammonia oxidation/
Nitrous oxide emission/
Nitrogen loss
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